textproduct: Quad Cities

KEY MESSAGES

- Mostly cloudy skies will continue through the upcoming weekend with spotty light rain showers. Precipitation chances increase further towards mid-week next week when a larger and wetter system moves in.

- Temperatures will continue to be cooler than average into the weekend, moderating back to seasonable or even slightly above normal levels next week.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 1150 AM CDT Thu Sep 24 2026

The generally cloudy weather pattern looks to continue today through at least Saturday. Partly to mostly cloudy skies today were seen thanks largely to a stout low-level thermal inversion in the 850-700 mb layer, which can be seen on the 24.12z ILX RAOB sounding. An extension of a large high pressure system anchored over southern Quebec Canada will break down overnight tonight, allowing a weak mid- level shortwave to ride mid-level ridging and move into our area. The latest suite of high-res model soundings suggest a layer of dry air near the 800 mb level should help inhibit rainfall accumulations tonight, but this layer should erode in time Friday morning as higher Pwat values of around 1.4 to 1.7 inches builds in after sunrise Friday. Chances of rainfall will peak around 30-60% for any given hour from midnight tonight through Friday afternoon. A lack of instability and robust nocturnal low-level jet will help keep any thunderstorms at bay. As far as rainfall totals are concerned tonight through Friday afternoon, amounts are generally expected to be a tenth of an inch or less, with exceedance probabilities of a tenth around 30-60% (highest over southeast Iowa into northeast Missouri). Due to persistent cloud cover, low temperatures will generally hover near 60 tonight, and highs Friday in the middle 60s.

Friday night should see a brief lull precipitation chances before increasing during the daylight hours Saturday (more on that in the long term section). Friday night lows should be similar to what they're expected to be for tonight, although some upper 40s to lower 50s are possible over northwest Illinois where clearer skies are expected.

LONG TERM /SATURDAY THROUGH THURSDAY/

Issued at 1150 AM CDT Thu Sep 24 2026

An active weather pattern continues for this weekend into mid-week next week. First, another mid-level shortwave will attempt to build in from the west Saturday into Saturday night. An interesting signal in the global deterministic models is for the QPF to build in to our far western forecast area but struggle to progress eastward. The suspicion is that dry easterly flow, with a lingering high pressure ridge axis near Lake Michigan, will help inhibit precipitation expansion eastward. This would suggest that the footprint for a wetting rainfall in our area would be smaller, and this is backed up by the latest NBM exceedance probabilities of a quarter inch or more of rain, highlighting 50-80% chances along and west of US Highway 218. The signal is for the precipitation to wane Sunday morning as mid-level ridging reinvigorates and weakens the shortwave forcing. With the cloud cover and rain in place, temperatures will feel cooler than average, with highs in the lower to middle 60s for most Saturday and Sunday.

Sunday night through Monday appears likely to be a dry period thanks to high pressure dominating over the region. Partly to mostly sunny skies and southeasterly flow Monday should result in the return of upper 60s to lower 70s for high temperatures.

This period of dryness will come to an end mid-week as a larger system builds in sometime around late Tuesday/Wednesday. A longer wave trough, with models showing a strong tropical connection to the systems in the eastern Pacific, should translate through the area, although the exact timing of associated precipitation remains uncertain. However, there is a strong signal for abundant moisture with this system, with Pwat values of around 1.5 to 2 inches. Exceedance probabilities of 1.6 inch Pwats are around 50-70% per the latest LREF ensemble, supporting a period of heavy rainfall potential. Now, it remains unclear how long this period of rainfall will last into Wednesday, given differing end times of precip per the GFS/ECMWF/CMC global model solutions as some guidance shows a large progressive longer wave trough sweeping across the mid-CONUS versus a slower cut-off low with multiple rounds of rains mid to late week. The latter scenario would be more concerning for heavy rainfall/flash flooding, given wet antecedent conditions, so this mid-week system does bear watching.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 642 PM CDT Thu Sep 24 2026

Another BKN stratocumulus deck is in store for tonight. Ceilings should remain VFR around 3-5 kft through 11 UTC before light rain showers try to move in from the west. Dry mid levels will limit coverage to 30-50%, so only PROB30s have been included at BRL, CID, and MLI until confidence in timing improves. Regardless of showers, ceilings are expected to lower to MVFR conditions areawide by mid-morning and last through at least 22 UTC. Latest guidance is showing ceilings staying between 1-3 kft, but there is a 30% chance that CID and MLI could see brief moments of IFR ceilings mid-morning into the early afternoon. Otherwise, winds will stay easterly around 3-7 knots.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.